Abstract
Levels of populated following the decay of the ground state of have been investigated by γ-ray and conversion electron singles, γ-ray multispectral scaling, γ-γ and γ- coincidence, and γ-γ angular correlation measurements. These data have been used to establish the population of eight excited levels of , to confirm the assignment of the 2695-keV level, and to determine a half-life of 5.4(1) s for . The deduced beta transition strengths establish the decay to the ground state, with logft of 5.6, as one of the fastest first-forbidden decays known and support the notion of double subshell closure at Z=40 and N=56. The observed strong hindrance of transitions to excited states is indicative of shape coexistence. The observed level pattern of the band built on the state exhibits similarities to nearby vibrational-like nuclei having four valence protons and four valence neutrons. A four-particle, four-hole interpretation of the state is supported by the data, and we determine a deformation parameter, ∼0.2, for this intruder bandhead.
- Received 20 May 1987
DOI:https://doi.org/10.1103/PhysRevC.37.254
©1988 American Physical Society